However,assurfactantconcentrationreachestovaluesgreater
than CMC,nanoparticlepresenceleadstocompletelydifferent
behaviorandtheoil/waterinterfacialtensionbeginstogethigher
values(Region3).Theinterfacialtensioneventuallyreachesa
constant valuegreaterthantheoneobtainedbythesurfactant
itself (Region4).Theinterfacialbehaviorfortwolastregionscan
be wellillustratedthroughthe final dropshapesofsurfactant
solutions inoilmediumasrepresentedin Fig. 5. Itisvisually
inferredfromthependantdropshapesthatafteracertain
surfactant concentration(2000ppm),thedropsbegintogrow
and largerdropsmeanhigherinterfacialtensionvalues.Thedrop
shape andsizearesimilarforhighsurfactantconcentrationsdue
toconstantinterfacialtension.